1. Field of the Invention
The invention is directed to communication terminal equipment for wireless communication with transmission/reception base stations of communication systems. In particular, the invention relates to a communication terminal that recognizes a communication system having a selected base station and allocates a network address to the recognized communication system.
2. Description of Related Art
Such communication terminal equipment are known and work according to cordless communication standards such as DECT or mobile radio telephone standards such as GSM, DCS-1800 or CDMA standards. In addition to communication terminal equipment that communicate on a radio basis, there are also communication terminal equipment that communicate on the basis of infrared transmission. A communication system for a communication terminal equipment working according to the DECT standard is, for example, an individual transmission/reception base station operated as subscriber means at a public communication network having call control or a communication private branch exchange system having a plurality of transmission/reception base stations and an exchange means. Such communication terminal equipment according to the DECT standard can usually be logged on and operated at a plurality of such communication systems with respective access authorization. Communication terminal equipment that work according to one of the aforementioned mobile radio telephone standards are usually operated at mobile radio telephone networks. A communication system according to the aforementioned definition for mobile radio telephone terminal devices is such a mobile radio telephone network.
There are also communication terminal equipment for mobile radio telephone operation that can either be operated at two mobile radio telephone networks working according to different standards or in an operating mode as cordless terminal equipment according to a cordless standard and that can be operated in another operating mode as mobile radio telephone terminal equipment according to a mobile radio telephone standard. Such communication terminal equipment are usually referred to as mobile dual-mode communication terminal equipment.
When communication terminal equipment working according to one of the aforementioned principles is operated as subscriber equipment at a plurality of communication systems, then it can often be reached via different network addresses (telephone numbers) in these communication systems. A connection setup attempt addressed to one of these network addresses is unsuccessful because the communication terminal equipment is not logged on as reachable at a transmission/reception base station of the allocated communication system and the communication system at whose transmission/reception base station of the allocated communication system it is logged on as reachable has not communicated to any information the location of this communication terminal equipment to the communication system wherein the communication terminal equipment can be reached under this network address.
European Document No 0 738 093 A2, U.S. Pat. No. 5,506,887 and World Patent Document No. 97/21315 disclose a communication terminal equipment for wireless communication with one of at least two transmission/reception base stations of at least two communication systems in whose transmission/reception area the communication terminal equipment is located and at which it is logged on as currently ready to receive. The communication terminal equipment recognizes the communication system to which the transmission/reception station at which the communication terminal equipment is logged on as currently ready to receive belongs.
German Patent Document No. 43 43 335 A1 discloses a method for reaching telephone subscribers in fixed and mobile telephone networks upon employment of a mobile radiotelephone. Upon initial installation of the mobile radiotelephone, the local code or number of a fixed connection of the fixed telephone network and the direct-dial identifier of a telephone exchange system that is connected to a public, digitally functioning network is programmed into or stored in the program memory devices of the mobile radiotelephone. The program provided therefor is fashioned such that, dependent on where or, respectively, at which network access point the mobile radiotelephone is located at the moment, the rerouting required for the creation of the necessary connection code is implemented by manipulation of these numerals or numbers. In the “called” case, thus, a call control is provided that automatically activates a call redirection when the mobile radiotelephone is no longer located in the coverage area of a DECT network. This call redirection can also be in turn cancelled at any time when a reachability of the mobile radiotelephone is not desired.